4 Replies Latest reply on Sep 2, 2016 3:32 AM by Beauty_and_dBest

    Duplicate IP in /etc/hosts


      Hi All,


      EBS R12.1.3




      I check out /etc/hosts and I see duplicate IP entries?

      app.oracle.com app dbc.oracle.com dbc




      Is this the cause why our RDA diagnostics failed?


      Kind regards?


        • 1. Re: Duplicate IP in /etc/hosts

          nslookup will just resolve the first entry, ie app.oracle.com app, but the second entry will be skipped over, so when you do a nslookup for app.oracle.com, it will succeed, but a nslookup for dbc.oracle.com would fail.


          If you want to resolve both names with the same IP, then you need to merge them into the same entry, ie


 app.oracle.com app dbc.oracle.com dbc


          • 2. Re: Duplicate IP in /etc/hosts

            Thanks Handat 


            So this is allowed in EBS? or This is not the reason why RDA test failed for this item?


            We have some failed items for our RDA health check

            Health Check/Validation for "Oracle E-Business Suite Release 12 (12.1.1) Preinstall (Linux x86 and x86_64)"


            One is

            A00420DNS LookupFAILEDnslookup IP_address
            A00420This rule checks that the host is registered correctly in the Domain Name Server (DNS).nslookup IP_addressThe DNS server failed to resolve the name using IP address.




            Kind regards,

            • 3. Re: Duplicate IP in /etc/hosts

              I am not sure what test RDA is performing. A DNS test usually check that a hostname resolves correctly to an IP, but it might go further and also do a reverse lookup, ie do a lookup on the IP and get the hostname back. This test would fail in many systems that don't have reverse dns configured. RDA might be doing this test as it appears to be checking for the IP address, ie


              DNS LookupFAILEDnslookup IP_address




              nslookup app.oracle.com should be successful and return the IP address, but nslookup will not resolve if its just added to /etc/hosts

              It needs to be registered in the DNS server that is pointed to in  /etc/resolv.conf


              Check with your network admin whether your DNS supports reverse lookup and if so, whether it has the appropriate zone config with the arpa entries. FYI, Amazon R53 DNS server does not support reverse lookup in case you are using that.

              • 4. Re: Duplicate IP in /etc/hosts

                Hi Bashar,


                We have also another instance in EC2. But it is working good.

                Well maybe it will fail RDA test as well, but we do not have problem with it


                Still it has error in nslookup?


                [root@erp ~]# cat /etc/hosts

         localhost localhost.localdomain localhost4 localhost4.localdomain4

       erp.oracle.com erp


                [root@erp ~]# cat /etc/sysconfig/network







                [root@erp ~]# cat /etc/resolv.conf

                # Generated by NetworkManager

                domain ec2.internal

                search ec2.internal oracle.com


                [root@erp ~]# nslookup erp.oracle.com




                ** server can't find erp.oracle.com: NXDOMAIN




                So how what do I do to make it pass?